text: According to the location of the rotaxanes units, polyrotaxanes can be mainly divided into two types: main chain polyrotaxanes, in which the rotaxane units locate on the main chain (axis), and side chain polyrotaxanes, in which the rotaxane units are located on the side chain. Corresponding polypseudorotaxanes can also be divided based on the same principle: main chain polypseudorotaxnes or side chain polypseudorotaxanes, in which there is no stopper at the ends.
  In both main chain polyrotaxanes or side chain polyrotaxanes, the unique feature from other polymers is the potential for different motion of the ring unit relative to the string units. Because the shape and location of the assembly are capable of showing different responses to changes in temperature, pH or other environment conditions, polyrotaxanes have many distinctive properties.